MYTUTOR SUBJECT ANSWERS

Why do transition metals form coloured solutions?

White light is a mixture of different colours of light (e.g red, green and blue) and each colour has a different wavelength. For something to have colour, it needs to absorb certain wavelengths (or colours) of light. What's left over is what we see. So how do transition metals do that?

When they dissolve in solution, they don't exist as isolated ions but are surrounded by ligands (in aqueous solutions they're water molecules). These ligands donate a pair of electrons to the positive metal ion in a dative covalent bond. For example, iron forms [Fe(H2O)6]2+ which is pale green. These ions are called complex ions.

All transition metals have electrons in their d orbitals, which are electrostastically repelled by those donated by the ligands. Since d orbitals have different shapes and orientations, they're not all repelled to the same extent: for an octahedral complex ion, the ligands are placed at the 6 corners of the octadedron. The dz2 and dx2-y2 are pointing to those corners and so are repelled a lot. The other three d orbitals don't point directly towards the ligands and so are repelled less. Therefore, the dz2 and dx2-y2 orbitals are at a higher energy than the other three, and so an energy gap is created, called d orbital splitting.

When light shines on the solution, wavelengths of light that have an energy equal to the energy gap between the two sets d orbitals take electrons in the lower energy orbital to one at the higher energy level. The wavelengths left behind are what we see!

“I'm currently studying medicinal chemistry and pharmacology at the University of Liverpool as part of an 'integrated masters' course designed to fast track students interested in a chemistry as a profession or continuing study to a PhD...”

“Hey,You've made it this far, now read a little about me and what you can expect, and hopefully get in touch.About me:I am reading chemistry at Oxford University and am currently working on a project to design a new type of spectr...”

“Hi! I'm a second year Natural Science student at the University of Exeter. I
love all things science, and enjoy sharing what I know about it with others.
For my GCSEs and A Levels, I found worked examples and practice questions are
ke...”

About the author

“Who are you?I'm a chemistry student at Durham University who has a (slightly nerdy) passion for not just chemistry but all things science. During my A-levels I really got gripped by how interesting studying the natural world is, and ...”

Sign up

Get in touch

Leave your contact details below and we will get back to you with more information

Your full name*

Email Address*

Organisation Name*

Your phone number*

Request sent

We have received your email and will be in contact soon.

MTW tutor guarantee

Every tutor on our site is from a top UK university and has been personally interviewed and ID checked. With over 7 applications for each tutor place, you can rest assured you’re getting the best.

As well as offering free tutor meetings, we guarantee every tutor who has yet to be reviewed on this site, no matter how much prior experience they have. Please let us know within 48 hours if you’re not completely satisfied and we’ll refund you in full.

Happy students

Every time a student and parent lets us know they have enjoyed a tutorial with a tutor, one 'happy student' is added to the tutor's profile.

mtw:mercury1:status:ok

Version details

Version:

3.26.0

Build:

b023f5b4f270

Time:

2016-12-05T16:44:39Z

Message sent

Your message has been sent and you'll receive an email to let you know when responds.
Tutors typically reply within 24 hours.